Notable park features include numerous waterfalls along the glacially formed Yosemite Valley of the Merced River[?] and the majestic Half Dome and many steep cliffs for rock climbing. These cliffs are more than 3000 feet in height.

Most park visitors fail to realize the scale of the cliffs in Yosemite Valley because they just look like normal rocks from a distance.
Many people would be awed by the sheer size of those rocks if they were able to spot some ant-like rock climbers hanging on the cliffs.
Another way to get a sense of the scale of the cliffs was to look for full size trees on the top of the cliffs which appear like hairs on the rocks.

The park covers large areas of wilderness. However, the majority of tourists stay within or around the Yosemite Valley which is only a tiny fraction of the national park.

To the north of Yosemite Valley is Hetch Hetchy Valley[?], which was considered by many, including John Muir, to be nearly identical in beauty and significance to Yosemite Valley. The valley was flooded in 1923 by the O'Shaughnessy Dam[?] blocking the Tuolumne River[?] to form the Hetch Hetchy reservior. The dam supplies water and cash (from electricity sales) to the San Francisco area. Congress authorized the O'Shaughnessy Dam in 1913. Passage of the law is said to have led to John Muir's death (from despair).